1. Field of the Invention
The present invention relates to an apparatus for fixing a printed circuit board on a worktable of an automatic electronic components insertion machine by positioning pins. More particularly, the present invention relates to an apparatus for fixing a printed circuit board to a predetermined position on a worktable of an electronic components insertion machine by automatically changing the relative position of the positioning pins in response to a change in the size of the printed circuit boards fed onto the worktable.
2. Description of the Related Art
Diverse automatic electronic components insertion machines are conventionally used for automatically planting and fixing electronic components on a printed circuit board which is fed or supplied automatically onto a worktable of the insertion machine. The automatic electronic components insertion machine is provided with an insertion head by which leads of electronic parts or components are successively inserted in or assembled on a printed circuit board automatically supplied onto the worktable capable of moving in two mutually orthogonal directions in a horizontal plane and rotating about a vertical axis so as to position mounting holes of the printed circuit board in alignment with the axis of the insertion head. The insertion head inserts leads of each electronic part or component from above the printed circuit board into the corresponding mounting holes of the printed circuit board. Therefore, the worktable is always provided with a pair of positioning pins for fixing a printed circuit board to a predetermined position on the worktable when the printed circuit board is automatically fed onto the worktable. However, the conventional automatic electronic components insertion machines are designed and constructed in such a manner that a number of printed circuit boards having an identical size are continuously processed in the mass production style. That is, there are no frequent changes in the size of the printed circuit board. Accordingly, there is no need for a means for automatically changing the relative position between the pair of positioning pins for fixing a printed circuit board. When printed circuit boards having a different size are to be processed by the insertion machine, the relative position between the pair of positioning pins is manually changed so as to fit the change in the size of the printed circuit boards.
On the other hand, in recent electronic microcomputers, electronic business machines, and electric household appliances, large numbers of electronic units incorporating therein printed circuit board assemblies are employed. Therefore, assembling of the printed circuit boards, including automatic insertion of electronic parts or components into a printed circuit board must be carried out by a flexible manufacturing system. Thus, in the automatic electronic components insertion machine, there is a strong demand for an improvement in the fixing of the printed circuit board on the worktable by the use of the pair of positioning pins; namely, the relative position of the positioning pins can be automatically changed in response to a change in the size of the printed circuit boards without necessitating a manual operation by the operators.